1. Field of the Invention
This invention relates generally to laser marking system, and in particular, to a laser marking apparatus and method for marking the surface of a workpiece with a laser beam.
2. Description of the Prior Art
In recent years, the use of lasers in hard disk surface processing is gaining popularity. Laser pulses have already been successfully used to create landing zones with improved tribology performance for the data transducing heads. Lasers have also been identified as a viable tool for the marking or labeling of hard disk surfaces. There are several occasions where disks need to be individually labeled. For example, a hard disk may contain markings indicating the number of reworks it has undergone, to assist the drive manufacturers in determining if a particular disk is suitable for further rework. Marking on an individual disk not only helps to classify the disk but also allows the drive and media manufacturers to identify the product type and trace the origin of the disk should mixing occur. The media manufacturers can more easily and reliably trace faults that result in disk failure if relevant information is tagged to individual disks.
Currently, there are a few methods of marking the finished disks. Some users mark on the disk surface using a scriber. The scriber actually cuts into the delicate disk surface, abrading and damaging the top layers of the disk. Alternatively, disk marking can be carried out using some forms of ink. Ink marking may use either a jet of the liquid ink or simply a pen with a felt tip to transfer the inscription onto the disk surface. However, ink films can deteriorate with time and give rise to contamination. A disk marking method that is both non-contaminating and non-damaging is needed. The marking method also needs to be fast and efficient in order to be adopted by the manufacturing industry.
It is therefore an object of the invention to provide an apparatus which uses a laser to produce visible deformations on the surface of a workpiece, especially a hard disk magnetic storage media workpiece.
It is another object of the invention to provide a method and apparatus for speedily and precisely marking hard disk magnetic storage media with a laser in a way such that surface deformation is visible, yet the protective carbon layer of the disk is intact and free of ablation.
It is yet another object of the invention to provide a method and laser apparatus for inducing surface deformation for the marking process without introducing contamination to the disk surface.
According to one aspect of the present invention, there is provided a laser beam generator, a beam conditioning module comprising a rotatable optical plate and a beamsplitter, a beam monitoring module, a beam steering module, and a materials handling unit to handle workpieces being marked. A beam from the laser generator is passed through a rotatable optical plate and a beamsplitter in the beam conditioning module, and a sample of the beam is passed to a beam monitoring module where the fluence of the beam is determined, and if desired, the rotatable optical plate can be rotated to vary the fluence of the conditioned beam leaving the beam conditioning module. The conditioned beam is passed to a beam steering module, which directs the beam to the surface of a workpiece held by the materials handling unit.
An advantage of the present invention is that a workpiece such as magnetic storage media can be marked using a laser without ablation of the protective carbon layer, and thus no additional cleaning or processing step is required before the storage media is used.
Another advantage of the present invention is that the fluence of a laser marking beam can be adjusted without changing the power setting of the laser itself.
A further advantage of the present invention is that flashback of the laser beam from the workpiece or beamsteerer is prevented.